Hydraulic system and mechanical latch therefor

ABSTRACT

The present invention comprises a pressure system and latching means for determining and controlling movement of a truck-cab relative to its tractor, and, in addition, for latching the two structures together, for translational movement. The pressure system includes means not only for unlocking the latch employed but also for controlling movement and disposition of a cab relative to its tractor frame. The latch means, itself, is of importance in a variety of contexts, to provide for control at a distance of unlatching and latching together two given structures.

United States Patent [191 Brimhall 1 Mar. 19, 1974 HYDRAULIC SYSTEM ANDMECHANICAL LATCH THEREFOR [75] Inventor: Ray S. Brimhall, Salt LakeCity,

Utah

[73] Assignee: Walker Bank and Trust Company [22] Filed: Apr. 29, 1968[21] Appl. No.: 732,484

[52] U.S. Cl 296/28 C, 180/89, 292/110, 296/35 R, 298/22 [51] Int. ClB62d 33/06 [58] Field of Search 296/28, 35, 35.1; 180/89; 292/110, 144,201; 294/83, 83.1

[56] References Cited UNITED STATES PATENTS 1,983,280 12/1934 Flowers298/22 2,749,175 6/1956 King et al. 298/22 2,647,789 8/1953 Chayne292/144 X 2,868,583 1/1959 Harbers et al. 298/22 X 2.939.541 6/1960Smalley ISO/89 Primary Examiner-Benjamin Hersh Assistant Examiner-JohnA. Pekar Attorney, Agent, or FirmDavid V. Trask 5 7] ABSTRACT Thepresent invention comprises a pressure system and latching means fordetermining and controlling movement of a truck-cab relative to itstractor, and, in addition, for latching the two structures together, fortranslational movement. The pressure system includes means not only forunlocking the latch employed but also for controlling movement anddisposition of a cab relative to its tractor frame. The latch means,itself, is of importance in a variety of contexts, to provide forcontrol at a distance of unlatching and latching together two givenstructures.

13 Claims,-7 Drawing Figures m nimum 1 9 1914 3797.882

sum 1 or z PATENTEDIMR 19 m4 SHEET 2 BF 2 n wv 7/1 I HYDRAULIC SYSTEMAND MECHANICAL LATCH THEREFOR The present invention relates to pressuresystems and latches therein, and, more particularly, to a new andimproved pressure system and pressure-operated latch therein which canaccomplish a variety of desirable objectives. The invention isespecially applicable in the trucking art wherein cabs are releasablylatched to their frames and, upon unlatching thereof, are pivotable withrespect to their frames for re-work operations.

. In the past a number of problems have presented themselves inconnection with cabs pivoted to tractor frames. There is the everpresent problem of appropriately lifting the cab, relative to the frame,for re-work and maintenance operations. Customarily, these cabs arepivoted to the frame, and suitable hydraulic means are used toselectively lift the cab relative to the frame and also to permit itsdescent. In the inventors copending application entitled Hydraulic Valveand Systern, filed Dec. 2, 1965, Ser. No. 530,242, which now US. Pat.No. 3,430,653 is fully incorporated herein by way of reference, theinventor has solved a number of problems in connection with cab lift,providing a novel four-way valve and system. The valve employed permitsmetered descent on both sides of the cab pivot in a very desirable andfunctional manner. The present invention is an extension of the latterinvention, and in addition solves another problem area, wherein thelatching means used to releasably latch the cab to the tractor frame ispressure-operated in the present invention and, indeed, is actuated bythat same system which controls the movement of the cab itself. Byapplicants system the unlatching of the cab is or can be accomplished ata remote point and in a very easy manner; the latch is spring-controlledand is made in such a way that latch-release is accomplished prior tothe actual pressure lifting of the cab. The latch means is soconstructed and arranged that cab descent automatically accomplishes cabrelatch to its tractor frame, and this without any further manipulationof the artisan, if so desired.

Accordingly, the principal object of the present invention is to providea pressure-operated latch.

A further object is to provide a pressure system incorporating apressure-operated latch.

A further object is to provide a pressure system for moving one objectrelative to another and, additionally, for accomplish an unlatching ofone object relative to the other prior to such movement.

A further object is to provide an improved pressureoperated latch forcab-tractors.

An additional object is to provide a pressure system for raising andlowering cabs relative to their tractor frames and, additionally, forautomatically unlatching the cab relative to the frame immediately priorto cab movement control.

A further object is to provide in a pressure-operated latch suitablemeans for automatically displacing the latch upon pre-determinedextensions thereof.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may best be understood byreference to the following description,

taken in connection with the accompanying drawings in which:

FIG. 1 is a side elevation, partially section, of latching meansconstructed in accordance with the present invention.

FIG. 2 is a view similar to FIG. 1 but illustrates the latching means ashaving become unlatched from its retainer through extension of suchlatching means under pressure.

FIG. 3 is similar to FIGS. 1 and 2 but illustrates a closing of thelatch means relative to its retainer to accomplish a re-latching of themechanical structure involved.

FIG. 4 is a horizontal section looking downwardly and is taken along theline 44 in FIG. 1.

FIG. 5 is an enlarged fragmentary elevation taken along the line 55 inFIG. 1.

FIG. 6 is an elevation, partially in schematic form, of a pressureincorporating the principles of the present invention and the latchthereof; in FIG. 4 the system is shown as lifting a cab relative to itsframe.

FIG. 7 is a view similar to FIG. 6 and illustrates a return of a cab toits frame; in FIG. 7 the latch and retainer bar are reversed relative totheir mountings to the tractor frame and cab, this to illustratealternate forms of the invention.

In FIGS. 1 and 2 latch means 10 is pressure-operated and includescylinder 11 and piston 12, the latter being provided with piston rod 13.Cylinder 11 includes threads 14 which threadedly engage threads 15 ofthe upper portion 16 of housing 17. If desired, a shoulder may beprovided against which the end 19 of cylinder 11 may abut. ConventionalO-ring seals may be provided for the piston, or the latter may be simplymachined for close tolerance fitting within the bore of cylinder ll.

Threaded into cylinder 1 l is upper portion 24 having wrench flats 25 towhich a conventional wrench may be applied to secure the cylinder intohousing 17. The threaded end fitting 29 threadedly engages the internalthreaded bore 27 of portion 25. Threaded end fitting 29 may comprise ahydraulic or pneumatic fitting to which conduit 30 is secured.

Piston rod 13 selectively abuts flange member 31, the latter beingprovided with circular flange 32 and bifurcated flange extension 33. Thelatter may take the form of a pair of arms 34 across which and betweenwhich is mounted a pivot pin 35, through corresponding arm apertures 36.

Housing 17, in addition to including upright portion 16, is providedwith opposite side walls 17 having flanges 38. The latter includes aplurality of mounting apertures 39 for mountingly receiving the mountingplate 40. Attachments 4] (not shown in FIG. 4) may be employed toaccomplish the securement, if desired. Further, possible additionalmounting holes, not shown, may be provided to secure the combination tothe frame of a tractor or cab, for example. Mounting plate 40 willpreferably include an upstanding stop 42 and also upstanding camabutment 43. Members 42 and 43 are preferably made integral with theplanar portion 44 of mounting plate 40. Mounting plate 40, of course,will include a slot 61 for translationally receiving hook portion 46 oflatch 45.

Latch 45 enjoys a hook configuration, including hook portion 46 and anelongate portion 47. Portion 47 terminates in cam portion 48, the latterincluding a central aperture 49 for pivotally receiving pivot pin 35.Cam portion 48 includes an extension 50 providing surface 51 whichabutingly engages abutment 43 of mounting plate 40. Accordingly, it isseen that an upward movement of piston 12 provides an upward thrustingof latch 45 and, ultimately, engagement of surface 51 with abutment 43.This causes a counterclockwise rotational displacement of latch 45 aboutthe axis of pivot pin 35.

Returning now to the completion of the latch means structure, it will beseen that a compression spring 53 is disposed between flange member 31and mounting plate 40, the ends of the spring thrusting against the samein opposite directions. An upwardly extending lip 54 may be included inthe design of flange 32 so as to offer a seat for the spring 53. A latchreturn spring 55 is mounted to pin 56 disposed between arms 54. Oppositeextremities of the return spring 55 engage flange 32 and surface 57ofcam portion 48. This is to urge the latch 45 in a clockwise direction,for proper ultimate engagement of a retainer bar 57 as hereinafterexplained. Stop 42, if used, may serve as a forward positioning stop oflatch 45 to stop the movement of latch 45. It is noted that latch 45includes the hook portion 46,the latter having a cam surface 58. Hence,upon relative movement of retainer bar 57 toward latch means 10, (seeFIG. 3) or vice versa, the retainer bar 57 may thrustingly engage camsurface 58 so as to urge the hook out of the way and thus allow there-latching of retainer bar 57 by hook portion 46 in the mannerhereinafter set forth.

The structure as thus far described operates as follows: The latch meansl-is pressure-operated, hydraulically or pneumatically, with chamber Cof cylinder 11 receiving the pressure fluid through conduit 30. In theabsence of the existence of pressure chamber C, then compression spring53 returns flange 32 downwardly so that piston 12 assumes a lowerposition within cylinder 11. At this point it is presumed that thehookconfigured latch 45 is engaged with retainer bar 57. (In thisconnection, when the invention is utilized with a cab lift on a tractor,then the latch means will either be mounted to a cab and the retainerbar to the frame of the tractor, or vice versa). Assume at this pointthat there is to be an unlatching of the cab relative to the tractorframe so that there will be enabled a mutual vertical separation ofretainer bar 57 of latch 45. In such event pressure will be applied by aconduit 30 to chamber C so as to thrust the piston 12 upwardly. Thisproduces a corresponding upward movement of latch 45 so that the latterbecomes disengaged with retainer bar 57; at this point, and during thecontinued upward movement of latch 45 and bar 57 relative to latch means10, the cam surface 51 of latch 45 comes in contact with abutment 43.The latter produces a counter-clockwise movement of latch 45 through therelative downward urging of surface 51 by abutment 43. This is producedabout pivot pin 35. Thus, the latch 45 will be swung to the left ofretainer bar 57 so as to accomplish a separation between the planes ofrelative movement of retainer bar 57 and latch 45. When a desireddistance has been achieved relative to latch means of retainer bar 45,then pressure is reduced in chamber C and the latch 45 returns to itsvertical configurement under the pressure of spring 55 acting uponsurface 57.

For re-engagement of the latch 45 with retainer bar 57, the two areurged mutually together, either through the descent of the latch means10 to retainer bar 57, or vice versa (as shown), depending upon thestructure used, until surface 58 is engaged by the lower portion ofretainer bar 57. Further downward movement of the retainer bar 57against latch means 10 causes a camming to the left of hook portion 56,by retainer bar 57 pressing against surface 58. This camming actionovercomes the force of return spring 55 so as to rotationally displacelatch 45 to the left. Once retainer bar 57 rides over surface 58,thenthe retainer bar will fall in place within its cradle 60. Circularcompression spring 53 will then force flange 32 downwardly so as toprovide a pressured engagement between latch 45 and retainer bar 57.

It is believed that the use of mechanical means to serve as stop 42 andabutment 43 is preferred. As to the latter, i.e., abutment 43, and itsaction upon cam 48, hydraulic or pneumatic means may be used as well forlateral latch displacement of latch 45. However, simple mechanical meansas is shown in the preferred embodiment in FIG. 1 is preferred.

In FIG. 6, means provides for fluid flow between reservoir 67 andpressure source such as pump 68. (The embodiment illustrate use of theinvention with a hydraulic system. It will be understood that apneumatic system may be used equally as well.) Conduit 69 from pump 68is connected to port 70 of valve body 71 of positioning valve 72. Port73 is connected by suitable conduit 74 leading to cab lift cylinder 75,on one side of piston 76 thereof. Piston 76 includes a conventionalpiston rod 77 which is pivoted at 78 to cab 79. Cab 79 is itself pivotedto tractor frame 80 by pivot means 81.Valve port 82 is connected byconduit 83 to point 84 on cylinder on the opposite side of piston 76;the latter comprises a double-acting piston. Connected into the conduit74 by means of a tee is line 30 leading to cylinder 11 of latch means10. Latch means 10 is securely mounted to frame in the embodiment shownin FIG. 6. Port 83' of valve body 71 is connected by conduit 84 toreservoir 67. The valve gate 85 includes through-apertures 86 :and 87'for supplying re spective communication between ports 70 and 73 and alsobetween ports 82 and 83 (in the condition shown in FIG. 6). In thisconfiguration the ports are connected by the valve gate so that there isan upward movement of piston 76 and piston rod 77, corresponding to anupper or clockwise rotational displacement of cab 79.

The valve 72 is a three-position valve, with the position shown in FIG.6 indicating a forward-pressure action against piston 76 so as to liftthe cab 79, and, if desired, extend the same over-center. The valve 72will be so designed as shown, such that valve may assume a completelyturned-off position, as through a counterclockwise rotation of the valvegate relative to the valve body, so that no conduction through the valvewill occur.

FIG. 6 has illustrated a first conduction of the valve 72. FIG., 7indicates another conductive condition wherein the apertures 86 and 87'are moved out of registry with the valve body parts and wherein, inaddition, longitudinal surface slots 87 and 88 are brought into registrybetween ports 70 and 82 and also between ports 73 and 83. In such eventthere will be a flow as indicated by the arrows seen in FIG. 7, whereinthe slots 87 and 88 shunt the fluid across the valve gate in thepatterns indicated. In such event there will be a descent of piston 76and a corresponding progressive return of cab 79 to its originalhorizontal position.

Of course, where a pneumatic system is involved the pump 68 willcomprise a compressor, with the reservoir being simply the gaseous storeof outside atmosphere.

FIG. 6 illustrates the latch means 1.0 as being physically mounted bystructural means 89 to frame 80 of tractor T. In such event the retainerbar 57 of FIG. 1 may be securely affixed to cab 79 by any conventionalmeans.

In a slightly different embodiment of the invention, FIG. 7 illustratesthat the retainer bar 57 can be secured to the frame by conventionalmeans, whereas a latch means 10 will be secured to cab 79.

Whether the latch means 10 is secured to the frame of the towing vehicleor tractor, or whether it will be secured to cab 79, suitable apertures42 may be used for accommodating the attachments 89. In any event,retainer bar 57 may be welded or otherwise secured to structural membersS of frame 80 of tractor T. Handle H is shown schematically andindicates mechanical means which, if desired for use, may be used torotationally displace valve gate 85 within valve body 71.

The structure shown in FIGS. 6 and 7 operates as follows: Pressuredfluid as introduced through ports 70 is directed through port 73 to thelower side of cylinder 75, this to act upon piston 76 in urging the cabupwardly in a clockwise direction about its pivot 81. The latch means 10is so designed that it operates in the manner seen in FIGS. 1 through 3,so that the latch 45 will be disposed out of the way with respect toretainer bar 57, see FIG. 2, at that point at which sufficient pressurebuilds up within cylinder 75 to commence to move cab 79. This sequenceof operation can be controlled through the proper selection of thespring constant of spring 53, and this in turn will depend upon theweight of the specific cab involved. In any event, upon release of latch45 from retainer bar 57 as indicated in FIG. 2, the cab will be liftedand continuously progressed in a clockwise direction about pivot 81until the valve 72 is turned to Off position.

When descent of the cab is desired, then handle H is turned so that thevalve gate 85 rotates within valve body 71 to achieve the dispositionshown in FIG. 7. At this point the slots 87 and 88 come in line withports 70, 82, and ports 73, 83', so that there is a reverse-flowcondition produced. Thus, the piston 76 within cylinder 75 descendsdownwardly, permitting a return of the cab and a cammed engagement ofcam surface 58 of latch 45 with retainer bar 57 during such descent.After the descent is substantially completed the pressure of returnspring 55 returns latch 45 to the position shown in FIG. 1.

As seen in FIG. 6 there is substantially no pressure build-up on theoutput side of the valve, since the fluid return through conduit 74 ison the reservoir-side of the system. In such event, there will be nosideways displacement of latch 45 during cab descent. However, the valvecan take the configuration as shown in the inventors co-pending UnitedStates Patent Application, entitled Hydraulic Valve and System, Ser. No.530,242, filed Dec. 2, 1965, wherein there is a metering effect of thevalve by virtue of the latters construction on the output side of thevalve. In such event some pressure will exist in the chamber C ofcylinder 11 so as to produce an extension of the latch and its sidewaysdisplacement through the engagement of abutment 43 with cam surface 51of latch 45. In any event, upon complete descent the latch will returnto its initial position and engage the retainer bar, and also, in eitherevent, the construction provides means for accommodating a suitablere-engagement of retainer bar 57 with latch 45.

What is thus provided is a novel latching means, hydraulically orpneumatically operated, by which two structures, such as a cab and atractor frame, may be releasedly secured together. Release of onerelative to the other is hydraulically or pneumatically effectuated inthe manner as described. The latch means is ideally used in the four-wayvalve hydraulic system of the present invention, and in the hydraulicsystem shown in the applicants co-pending case above referenced, whereinthe pressure means used to actuate the cab lift is also employed toaccommodate latch release. Latch reengagement is easily facilitatedthrough the mechanical structure employed in the latching means and/orthrough proper pressure operation of the latter in accordance with theabove description.

While conceivably the piston rod 13 could be directly connected toflange member 31, it is preferable that both members be simplycooperatively, abuttingly disposed as indicated in FIGS. 1 and 3. Wherethe latch 45 is hooked to retainer bar 57 and the piston 13 withincylinder 11 withdrawn (by normal operation as through a reduction inoperating pressure and by the return spring 53) so as to allow for apossible ultimate spacing between the end of piston rod 13 and theadjacent surface of flange member 31 through normal vibration duringroad travel, then compression spring 53 provides for aspringingly-retained connection between the latch and the structure towhich retainer bar 57 is mounted. It will be noted that this is providedwithout any continuous bumping or other interference of the flangemember 31 with the piston or piston rod (which would otherwise causeseal wear), or surrounding housing 17.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects.

It is claimed:

1. A pressure-fluid operated latching mechanism including, incombination, a pressure cylinder, a housing means affixed to saidpressure cylinder, a piston disposed within said cylinder, meansconnected to said cylinder for selectively applying fluid pressure tosaid piston to translate the same forwardly within said cylinder, meansfor returning said piston rearwardly within said cylinder when saidfluid pressure is released, and latching means disposed in said housingmeans and cooperably disposed with respect to said piston, andextensible from and withdrawable toward said cylinder along the latterslongitudinal axis in response to movement of said piston, for releasablyengaging an external member, said housing means including means fortilting said latching means away from said longitudinal axis uponpre-determined travel of the latter.

2. Structure according to claim 1 wherein said latching means comprisesa concave hook-configured latch.

3. A pressure-fluid operated latching mechanism including, incombination, a pressure cylinder, a piston disposed within saidcylinder, means connected to said cylinder for selectively applyingfluid pressure to said piston to translate the same forwardly withinsaid cylinder, means for returning said piston rearwardly within saidcylinder when said fluid pressure is released, and latching meanscooperably disposed with respect to said piston, and extensible from andwithdrawable toward said cylinder in response to movement of saidpiston, for releasably engaging an external member, and wherein saidcylinder includes a housing, said piston including a piston rodprotruding into said housing, said mechanism including a flange memberdisposed within said housing and having a flange proximate said pistonrod and engageable thereby upon advancing movements by the latter, saidflange member also including a flange extension integral with saidflange and pivoted to said latching means at a pivot, said housingincluding reaction means disposed between said latching means and saidcylinder, said returning means comprising a compression spring operablydisposed between said flange and said reaction means.

4. Structure according to claim 3 wherein said flange member is separatefrom said piston rod and is constructed and arranged to be spacedtherefrom when said latch latches an external member and when said fluidpressure is released from within said cylinder.

5. Structure according to claim 3 wherein said mechanism includesintercooperable means respectively integral with said housing andlatching means for pivotally displacing said latching means in theprocess of the latters extension from said cylinder.

6. Structure according to claim 5 wherein said pivotally displacingmeans comprises an actuating protuberance integral with said housing anda laterally extending camming protuberance integral with said latchingmeans and actuatably engageable by said actuating protuberance, duringthe course of said latching means extension.

7. Structure according to claim 6 wherein said reaction means comprisesa plate, said actuating protuber ance being affixed to and upstandingfrom said plate toward said cylinder within said compression spring.

8. Structure according to claim 7 wherein said mechanism includes:return spring means for spring-biasing said latching means to saidflange extension about said pivot, and limit stop means for limiting thepivotal travel of said latching means about said pivot under thepressure of said return spring.

9. In combination, a tractor having a frame and a cab pivoted to saidframe, one of said frame and cab having a latchable member and theremaining having fluidpressurc operated latching means, fluid-pressureoperated means secured to and between said frame and said cab forpivotally, liftingly displacing said cab relative to said frame, saidfluid-pressure operated latching means being coupled to saidfluid-pressure operated means and being constructed for securing saidlatchable member by said latching means and, thereby, said cab to saidframe when fluid pressure is released, and, when fluid pressure isapplied, having first means for first separating said latching meansfrom said latchable member in the direction of the travel path of saidlatchable member when said cab is subsequently elevated and, then,having second means for subsequently moving said latching meanslaterally beyond the travel path of said latchable member as said cab isbeing elevated.

10. In combination, a tractor having a frame and a liftable memberpivoted to said frame, one of said frame and liftable member having alatchable member and the remaining having fluid-pressure operatedlatching means, fluid-pressure operated means secured to and betweensaid frame and said liftable member for pivotally, liftingly displacingsaid liftable member relative to said frame, said fluid-pressureoperated latching means being coupled to said fluid-pressure operatedmeans for securing said latchable member by said latching means and,thereby, said liftable member to said frame when fluid pressure isreleased and,,when fluid pressure is applied, having first means forfirst separating said latching means from said latchable member in thedirection of the travel path of said latchable member when said liftablemember is subsequently elevated and then having second means forsubsequently moving said latching means laterally beyond the travel pathof said latchable member as said liftable member is being elevated.

11. A pressure-fluid operated latching mechanism including, incombination, a cylinder, a housing affixed to and extending axially fromsaid cylinder, a piston operably disposed in said cylinder and having apiston rod extending from said cylinder within said housing, a flangemember disposed in said housing and having a flange disposed forengagement by said piston rod and a flange extension, a latch pivoted tosaid flange extension and extending beyond said housing, a compressionspring axially disposed with respect to said piston rod and operablydisposed between said flange and said housing and disposed within thelatter, said housing and latching means being provided withintercooperable means for pivoting said latching means relative to saidflange extension after a predetermined travel advancement of saidlatching means relative to said housing.

12. Structure according to claim 11 wherein said mechanism includesreturn spring means engaging said latching means for returning saidlatching means against prior pivoted displacement, and stop reactionmeans for limiting such return.

13. A pressure-fluid operated latching mechanism including, incombination, a fluid pressure cylinder having a central axis, a housingaffixed to said cylinder, a reciprocating piston disposed within saidcylinder and having an extension extending axially in one direction withrespect to said cylinder and within said housing, latching means forengaging an external member, said latching means being disposed in saidone direction beyond said piston extension, means cooperable with saidpiston extension and said latching means for advancing said latchingmeans in said one direction, during times of piston and piston extensiontravel in said one direction, and respective, mutually intercooperablemeans disposed on said latching meansand said housing for displacingsaid latching means laterally from the axis of said cylinder when apredetermined forward advance by said latching means has been reached.

1. A pressure-fluid operated latching mechanism including, incombination, a pressure cylinder, a housing means affixed to saidpressure cylinder, a piston disposed within said cylinder, meansconnected to said cylinder for selectively applying fluid pressure tosaid piston to translate the same forwardly within said cylinder, meansfor returning said piston rearwardly within said cylinder when saidfluid pressure is released, and latching means disposed in said housingmeans and cooperably disposed with respect to said piston, andextensible from and withdrawable toward said cylinder along thelatter''s longitudinal axis in response to movement of said piston, forreleasably engaging an external member, said housing means includingmeans for tilting said latching means away from said longitudinal axisupon predetermined travel of the latter.
 2. Structure according to claim1 wherein said latching means comprises a concave hook-configured latch.3. A pressure-fluid operated latching mechanism including, incombination, a pressure cylinder, a piston disposed within saidcylinder, means connected to said cylinder for selectively applyingfluid pressure to said piston to translate the same forwardly withinsaid cylinder, means for returning said piston rearwardly within saidcylinder when said fluid pressure is released, and latching meanscooperably disposed with respect to said piston, and extensible from andwithdrawable toward said cylinder in response to movement of saidpiston, for releasably engaging an external member, and wherein saidcylinder includes a housing, said piston including a piston rodprotruding into said housing, said mechanism including a flange memberdisposed within said housing and having a flange proximate said pistonrod and engageable thereby upon advancing movements by the latter, saidflange member also including a flange extension integral with saidflange and pivoted to said latching means at a pivot, said housingincluding reaction means disposed between said latching means and saidcylinder, said returning means comprising a compression spring operablydisposed between said flange and said reaction means.
 4. Structureaccording to claim 3 wherein said flange member is separate from saidpiston rod and is constructed and arranged to be spaced therefrom whensaid latch latches an external member and when said fluid pressure isreleased from within said cylinder.
 5. Structure according to claim 3wherein said mechanism includes intercooperable means respectivelyintegral with said housing and latching means for pivotally displacingsaid latching means in the process of the latter''s extension from saidcylinder.
 6. Structure according to claim 5 wherein said pivotallydisplacing means comprises an actuating protuberance integral with saidhousing and a laterally extending camming protuberance integral withsaid latching means and actuatably engageable by said actuatingprotuberance, during the course of said latching means'' extension. 7.Structure according to claim 6 wherein said reaction means comprises aplate, said actuating protuberance being affixed to and upstanding fromsaid plate toward said cylinder within said compression spring. 8.Structure according to claim 7 wherein said mechanism includes: retUrnspring means for spring-biasing said latching means to said flangeextension about said pivot, and limit stop means for limiting thepivotal travel of said latching means about said pivot under thepressure of said return spring.
 9. In combination, a tractor having aframe and a cab pivoted to said frame, one of said frame and cab havinga latchable member and the remaining having fluid-pressure operatedlatching means, fluid-pressure operated means secured to and betweensaid frame and said cab for pivotally, liftingly displacing said cabrelative to said frame, said fluid-pressure operated latching meansbeing coupled to said fluid-pressure operated means and beingconstructed for securing said latchable member by said latching meansand, thereby, said cab to said frame when fluid pressure is released,and, when fluid pressure is applied, having first means for firstseparating said latching means from said latchable member in thedirection of the travel path of said latchable member when said cab issubsequently elevated and, then, having second means for subsequentlymoving said latching means laterally beyond the travel path of saidlatchable member as said cab is being elevated.
 10. In combination, atractor having a frame and a liftable member pivoted to said frame, oneof said frame and liftable member having a latchable member and theremaining having fluid-pressure operated latching means, fluid-pressureoperated means secured to and between said frame and said liftablemember for pivotally, liftingly displacing said liftable member relativeto said frame, said fluid-pressure operated latching means being coupledto said fluid-pressure operated means for securing said latchable memberby said latching means and, thereby, said liftable member to said framewhen fluid pressure is released and, when fluid pressure is applied,having first means for first separating said latching means from saidlatchable member in the direction of the travel path of said latchablemember when said liftable member is subsequently elevated and thenhaving second means for subsequently moving said latching meanslaterally beyond the travel path of said latchable member as saidliftable member is being elevated.
 11. A pressure-fluid operatedlatching mechanism including, in combination, a cylinder, a housingaffixed to and extending axially from said cylinder, a piston operablydisposed in said cylinder and having a piston rod extending from saidcylinder within said housing, a flange member disposed in said housingand having a flange disposed for engagement by said piston rod and aflange extension, a latch pivoted to said flange extension and extendingbeyond said housing, a compression spring axially disposed with respectto said piston rod and operably disposed between said flange and saidhousing and disposed within the latter, said housing and latching meansbeing provided with intercooperable means for pivoting said latchingmeans relative to said flange extension after a predetermined traveladvancement of said latching means relative to said housing. 12.Structure according to claim 11 wherein said mechanism includes returnspring means engaging said latching means for returning said latchingmeans against prior pivoted displacement, and stop reaction means forlimiting such return.
 13. A pressure-fluid operated latching mechanismincluding, in combination, a fluid pressure cylinder having a centralaxis, a housing affixed to said cylinder, a reciprocating pistondisposed within said cylinder and having an extension extending axiallyin one direction with respect to said cylinder and within said housing,latching means for engaging an external member, said latching meansbeing disposed in said one direction beyond said piston extension, meanscooperable with said piston extension and said latching means foradvancing said latching means in said one direction, during times ofpiston and piston extension travel in said one direction, andrespective, mutuaLly intercooperable means disposed on said latchingmeans and said housing for displacing said latching means laterally fromthe axis of said cylinder when a predetermined forward advance by saidlatching means has been reached.